This invention relates to torqueable guide wires for use in guiding the placement of surgical instruments within a human or animal body during micro-invasive procedures.
The use of small needle systems in micro-invasive procedures in various medical fields has become routine because small gauge needles can pass through most of the anatomy without causing significant damage to the anatomy. Such needle systems are used extensively in cardiovascular procedures, and in the fields of radiology and urology, as well as in other medical fields.
Such needle systems generally include a relatively small guide needle which is used to guide a larger hollow catheter to the target within a human body or a veterinary body. The guide needle is directed to the proximity of the target using a hollow cannula. The cannula is inserted into the body and positioned, using fluorscopic techniques, for example, with its distal end contacting or adjacent to an organ or other mass within the body. The guide wire is then advanced through the cannula to the organ or mass and into the organ or mass to the target area. The cannula is then removed and the catheter is advanced over the guide wire and into the organ or mass to the target area.
Guide wires presently in use comprise, a composite structure including a relatively rigid wire or rod with a coil spring attached by welding or soldering to its distal end, defining a flexible or "floppy" tip for the guide wire. The "floppy" tip enables the guide wire to be directed through curving vessels and around obstacles as the tip of the guide wire is being advanced into an organ or other structure of the body without causing damage to the organ or body structure. To further enhance the flexibility of the distal end of the guide wire, the solid wire or rod may be tapered at its distal end with the coil spring extending over the tapered distal portion of the wire or rod and secured to the wire or rod at the point at which the taper begins.
In use, the guide wire is advanced to the desired location within the body through a cannula. The cannula is then removed and a catheter is advanced over the guide wire to the target within the body.
One significant shortcoming of known guide wires of the type including a coil spring tip, is that current techniques for securing the proximal end of the coil spring to the distal end of the solid wire, result in a discontinuity, such as a bump or gap or uneven surface at the junction of the wire and coil spring tip. This results from the way that the coil spring is positioned on the tapered shaft of the wire. Typically, the coil spring is slid onto the tapered distal end of the shaft and advanced until its proximal end assumes an interference relationship with the surface of the tapered rod. Because of this gap or uneven surface, as the guide wire is advanced through a cannula, the guide wire may "catch" on the cannula at its distal tip because of the discontinuity or uneven surface at the junction of the coil spring and the wire. This could result in the coil spring tip being broken off. Also, when the catheter is advanced over the guide wire, there is a tendency for the catheter to "catch" on this discontinuity or uneven surface, and with continued advancement of the catheter, the guide wire might be moved out of position.
Various attempts have been made to alleviate this problem. For example, in one arrangement, a teflon coating is provided over the entire extent of the guide wire. However, this arrangement does not eliminate the bump or extension at the junction point, but merely provides a smoother glide surface for the inner surface of the cannula.